Extinguishing chamber for oil circuit breaker having differential piston and gas filled space therein



July 14, 1964 H. FORWALD 3,141,083

EXTINGUISHING CHAMBER FOR OIL. CIRCUIT BREAKER HAVING DIFFERENTIAL PISTON AND GAS FILLED SPACE THEREIN Filed Oct. 23, 1961 Fig.3

United States Patent O 3 141 083 EXTINGUISHING CHAMRER FOR OIL CIRCUIT BREAKER HAVING DIFFERENTIAL PISTON AND GAS FILLED SPACE TI-IEREIN Haakon Forwald, Ludviira, Sweden, assignor to Allmiinna Svensira Elektriska Aktieholaget, Vasteras, Sweden, :1

Swedish corporation Filed Oct. 23, 1961, Ser. No. 146,889 Claims priority, application Sweden Nov. 8, 1960 Claims. (Cl. 200150) The present invention relates to an extinguishing chamber for oil circuit breakers. It is characterised in that a gas-filled closed space is arranged in the extinguishing chamber and limited by oil in a pressure chamber, a movable contact and nozzle-shaped stationary contact, which nozzle may be closed by the movable contact and through which the pressure chamber communicates with a space outside the extinguishing chamber when the contacts are separated. In the extinguishing chamber is also arranged a differential piston with a through-running channel for the movable contact, which differential piston limits a pump room communicating with the channel through a slot arranged in the piston and controlled by the movable contact.

An extinguishing chamber according to the above combines the high current breaking properties of a reaction chamber with the high voltage breaking properties of a differential chamber.

At a breaking the differential piston moves in a direction away from the stationary contact, so that the fiow rate of the oil from the pressure chamber towards the arc is successively weakened. This fiow may be strengthened by a first insulating intermediate wall provided with an opening for the movable contact being arranged to form an annular slot with the stationary contact, which slot communicates with the pressure chamber. In this way a slot is obtained as in a conventional reaction chamber, with constant and limited through-flow area. In the wall of the extinguishing chamber between the first intermediate wall and the differential piston, over-pressure valves could suitably be arranged.

In order to cause the oil to flow along the are at several different points, a second intermediate wall may suitably be arranged between the first intermediate wall and the differential piston, with a space to the first, which space, by means of openings in the wall of the extinguishing chamber, is arranged to communicate with the space outside the extinguishing chamber. These openings could be provided with over-pressure valves.

The invention will be better understood with reference to the accompanying drawings in which:

FIGURE 1 shows in cross section a circuit breaker embodying the invention;

FIGURE 2 shows a modified form thereof;

FIGURE 3 shows another modification;

And FIGURE 4 shows a further modification.

In FIGURE 1, 1 designates an extinguishing chamber immersed in oil. In the roof of the extinguishing chamher a cylinder 2 is attached which supports the stationary nozzle-shaped contact 3. In the lower part of the chamber a differential piston 4 is arranged. A pin-shaped movable contact 5 may, through a channel 6 in the differential piston, be moved into the stationary contact 3. The oil in the pressure chamber 7 below the gas-filled closed space 8 is kept permanently at the same level by oil level openings 9 being arranged in the wall of the extinguishing chamber 1. When the contacts are separated, the pressure chamber communicates through the nozzle of the stationary contacts 3 with a space outside the extinguishing chamber. The differential piston 4 limits a pump room 10 which communicates with the channel 6 through a slot 11 controlled by the movable contact 5. A spring 12 influ- Patented July 14., 1964 ences the differential piston 4 in a direction towards the stationary contact 3.

At a breaking action, the gas pressure generated by the are partly acts downwards on the larger surface of the differential piston 4 and partly upwards against the gasfilled closed space 8, the volume of which is thus compressed. At about the zero-point of the breaking current, the pressure in the gas around the arc drops and the compressed gas in the closed space 8 is now able to press oil and gas from the pressure space against the arc and out through the nozzle-shaped stationary contact 3. When the contact on its way downwards uncovers the slot 11 in the differential piston 4, pure oil from the pump room 10 also begins to stream through the slot 11 towards the lower part of the arc. The possibility now exists of extinguishing the are at relatively small contact distance and at high voltage, since the pure oil which flows from the pump room 10 into the channel 6 at the zero-point of the current, strengthens the insulation between the contacts considerably in comparison with the insulation in an arc channel which is filled along its whole length by a mixture of gas and oil, as is the case with a simple reaction chamber. When the breaking action is completed the differential piston 4 is returned to its initial position by the spring 12.

In the extinguishing chamber according to FIGURE 1, the distance between the differential piston 4 and the stationary contact 3 increases at a breaking action. The flow rate of the oil from the pressure space 7 and perpendicular to the arc is thus weakened. According to FIGURE 2 this may be corrected by arranging an insulating intermediate wall 13 provided with an opening 14 for the movable contact 5, between the stationary contact 3 and the differential piston 4 in such a way that, as in a conventional reaction chamber, an annular slot 15 with constant and limited through-flow area is formed between the stationary contact 3 and the intermediate wall 13.

In the extinguishing chamber shown in FIGURE 3, over-pressure valves 16 have been arranged in the wall of the extinguishing chamber between the intermediate wall 13 and the differential piston 4. This embodiment of the extinguishing chamber gives, at a breaking action, flows of oil along the are at three places, namely, through the nozzle contact 3, through the hole 14 in the insulating intermediate wall 13 and along the upper part of the channel 6 through the differential piston 4.

In the extinguishing chamber according to FIGURE 4, an intermediate wall 17 has been arranged between the intermediate wall 13 and the differential piston 4. The intermediate walls 13 17 are arranged at a certain distance from each other and the space between them, via openings 18, is in free communication with the space outside the extinguishing chamber. In an extinguishing chamber of this embodiment, thus, a flow of oil and gas is also obtained out through the openings 18. Overpressure valves could also be arranged in the extinguishing chamber according to FIGURE 4, in the wall of the extinguishing chamber between the intermediate wall 17 and the differential piston 4.

I claim:

1. Oil circuit breaker comprising an extinguishing chamber immersed in oil, a differential piston dividing said chamber into a pressure chamber and a pump space; the larger surface area of said piston limiting said pressure chamber, a stationary nozzle shaped contact arranged in said pressure chamber; said pressure chamber being partly filled with oil to a predetermined level, said last mentioned oil being in communication with the oil outside the extinguishing chamber through the open nozzle, a gas-filled closed space in the pressure chamber above said level; a channel through said piston and a movable contact arranged to pass through said channel in said piston to engage said stationary contact and close said nozzle, and a slot in said piston connecting said channel and said pump space and controlled by the movable contact for putting said pump space into communication with said channel when said movable contact moves toward said open position.

2. In a circuit breaker as claimed in claim 1, a first insulating intermediate wall arranged between said stationary contact and said piston, an opening in said wall for said movable contact, said intermediate Wall and said stationary contact forming an annular slot therebetween, said annular slot being in communication with said pressure chamber.

3. In a circuit breaker as claimed in claim 2, at least one over-pressure valve arranged in the wall of said extinguishing chamber between said first intermediate wall and said differential piston.

4. In a circuit breaker as claimed in claim 2, a second intermediate wall arranged between said first intermediate wall and said diiierential piston, with a space between said first and said second intermediate wall, said last mentioned space communicating through openings in the wall of said extinguishing chamber with the space outside said extinguishing chamber.

5. In a circuit breaker as claimed in claim 7, overpressure valves arranged in said openings in the wall of said extinguishing chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,409,723 Terry Oct. 22, 1946 3,010,003 Pucher Nov. 21, 1961 FOREIGN PATENTS 84,167 Sweden Aug. 27, 1935 796,191 France Jan. 17, 1936 1,028,662 Germany Apr. 24, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF "CORRECTION Patent No. 3,141,083 July 14, 1964 Haakon Forwald n the above numbered .pat-' that error appears i nt should read as It is hereby certified ent requiring correction and that the said Letters Pate corrected below.

Column 4, line 7, for the claim reference numeral "7" read 4 ed and sealed this 22nd day of December 1964.

Sign

(SEAL) Attest:

ERNEST w; SW IDER EDWARD J BRENNER ing Officer Commissioner of Patents UNITED; STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,141,083 July 14, 1964 Haakon Forwald s in the above numbered pat- It is hereby certified that error appear tters Patent should read as entrequiringcorrection and that the said Le corrected below.

Column 4, line 7 for the claim reference numeral "7" read 4 Signed and sealed this 22nd day of December 1964.

(SEAL) Ausr. ERNEST .swIoEa- EDWARD J, RENNER- Cbm'missioner of Patents Attesting Officer 

1. OIL CIRCUIT BREAKER COMPRISING AN EXTINGUISHING CHAMBER IMMERSED IN OIL, A DIFFERENTIAL PISTON DIVIDING SAID CHAMBER INTO A PRESSURE CHAMBER AND A PUMP SPACE; THE LARGER SURFACE AREA OF SAID PISTON LIMITING SAID PRESSURE CHAMBER, A STATIONARY NOZZLE SHAPED CONTACT ARRANGED IN SAID PRESSURE CHAMBER; SAID PRESSURE CHAMBER BEING PARTLY FILLED WITH OIL TO A PREDETERMINED LEVEL, SAID LAST MENTIONED OIL BEING IN COMMUNICATION WITH THE OIL OUTSIDE THE EXTINGUISHING CHAMBER THROUGH THE OPEN NOZZLE, A GAS-FILLED CLOSED SPACE IN THE PRESSURE CHAMBER ABOVE SAID LEVEL; A CHANNEL THROUGH SAID PISTON AND A MOVABLE CONTACT ARRANGED TO PASS THROUGH SAID CHANNEL IN SAID PISTON TO ENGAGE SAID STATIONARY CONTACT AND CLOSE SAID NOZZLE, AND A SLOT IN SAID PISTON CONNECTING SAID CHANNEL AND SAID PUMP SPACE AND CONTROLLED BY THE MOVABLE CONTACT FOR PUTTING SAID PUMP SPACE INTO COMMUNICATION WITH SAID CHANNEL WHEN SAID MOVABLE CONTACT MOVES TOWARD SAID OPEN POSITION. 